The precision manufacture of fasteners such as screws and the like having special features such as an anti-cross threading tip requires stringent quality control standards. The usual and established method for determining whether a part such as a fastener is manufactured within its specifications is to use an optical comparator. In an optical comparator, the part is place on a projector which projects a magnified silhouette of the part onto a screen. The screen has mounted on it a transparency prepared for the particular part in which the nominal part size and the allowable tolerances are shown at the appropriate magnification. Typically both the transparency and the part are magnified to ten times their normal size. The magnified projected silhouette of the part is compared against the standards shown on the projected transparency to determine if the part meets the manufacturing specifications.
The disadvantage of the optical comparator is that it is a very time consuming process to set up and make the comparison of the manufactured part with the standards.
It is desirable therefore, to provide a testing apparatus which obviates the need for visual comparisons between a manufactured part and its specification. Further it is desirable to test the manufactured part directly for its intended function.